Integrated circuit ("IC") devices are generally designed to have a molded plastic or ceramic packaging inside of which an electronic chip is housed. The package of modern generations of such IC devices are usually a flat rectangular shape, although some may have a flat, disk shaped, heat sink positioned on its top surface. In addition, IC devices typically have a plurality of tiny, fragile, conductive leads protruding out of the four sided perimeter of the package. The leads are wired to the electronic chip inside the packaging, and they form the electrical contacts by which the chip is connected to some external circuitry, often a printed circuit board.
After an IC device is formed, it often must be transported from the place of manufacture to the place where it will be integrated into a higher level assembly, such as the mounting of the IC device onto a printed circuit board. During transportation the device may be exposed to physical conditions, such as bumping, dropping, and vibration, which can damage the device if it is not properly protected. In particular, the fragile leads must be protected against being physically bent because the precise alignment of each lead is critical to successfully mounting the IC device on a printed circuit board. Such bending could easily occur if the IC device were to move around inside a transportation carrier as a result of the physical forces to which the carrier is ordinarily exposed while in transit.
The protection of the leads is especially important for IC devices which have the leads preformed so that they can be taken directly from the carrier in which they were transported and mounted onto the printed circuit board through an automated assembly operation that usually involves the use of robots. Such preformed, ready-to-be-mounted leads tend to be much more fragile and easily damaged than other leads that are formed, or bent, after they are transported to the board assembly site.
IC device carriers known in the art typically have a boxlike carrier with a nest for seating the body portion of the device and some means for keeping the body firmly seated in the nest during transportation. As shown in U.S. Pat. No. 4,881,639, issued to Matsuoka et al. on Nov. 21, 1989, one IC device is seated in an accommodating section. It is held in position by four engaging claws which hold the four corners of the device. The engaging claws are mounted on torsion bars which twist to enable the device to be inserted and extracted from the carrier. One disadvantage of this approach is that the engaging claws must be precisely configured to mate with and secure the four corners of the IC device. Therefore, changes in the device configuration, which have the effect of moving the leads closer to the corners of the device, may necessitate the reconfiguration of the carrier, if the positioning of the original claws causes interference with the new lead positions.
In fact, many successive generations of IC devices have demonstrated a general progression toward increasing the number of leads, which is referred to as the "pin count", on such devices. Increasing the pin count has a tendency to move the leads closer to the corners of the device because more leads are packed into the same amount of perimeter space. Consequently, the carrier shown in Matsuoka may also have the disadvantage that successive generations of devices may have less corner space by which the chip may be grasped by the engaging claws. With less space available, the contact portion of the engaging claws will have to be made smaller, which may make it less reliable and more subject to breakage.
Another carrier, shown in U.S. Pat. No. 4,564,880, issued to Christ et al. on Jan. 14, 1986, similarly provides a nest like structure, generally referred to as a "retainer", positioned in the bottom section of the carrier for the seating of the body of the device. In this instance, the device is clamped in place between a supporting lip and the hemispherically shaped tip of a holding pedestal. This approach relies upon the spring action produced by the resilience of the material from which the carrier is constructed to keep the IC device clamped between the holding pedestal and the support lip.
According to Christ, when the body of the IC device is exposed to moderate external forces, those forces tend not to harm the IC because the body possesses the material property of rigidity. On the other hand, the tip of the hemisphere of the carrier shown in Christ is the only point of contact on one side of the device for holding the device in place, and it provides a point about which the body of the IC device may pivot. Therefore, if the carrier shown in Christ was exposed to robust transportation conditions, the pivot point of the tip together with the resilient characteristics of the material out of which the carrier is made could result in the device unseating itself from the nest.
What is needed, therefore, is an IC device carrier which is capable of protecting the device during transportation in a robust environment, and overcomes the disadvantages of the prior art.